A solar power collection system is basically a heat based engine. For any heat based engine, heat is supplied and heat is exhausted. The usable work generated by an ideal heat engine is the difference between the heat supplied and the heat exhausted. In a heat engine, work is extracted during the flow of heat through the engine from a hot supply side to a point of lower thermal energy called a cold side. While heat supplied is considered the fuel of the system, heat rejection is imperative to avoid heating up the cold side to the point that it matches the hot supply side, causing the engine to cease operating. The efficiency of a heat engine is the percentage of how much initial supply side heat is converted into useful work, with the remainder to be exhausted, or rejected.
For a typical heat engine, fuel is brought in and converted into thermal energy for supply heat must be pushed beyond the heat engine, or the engine will heat up and cease to operate. Most heat rejection systems employ water to accomplish this, such as steam evaporation. Cooling of the steam from a vapor to a liquid requires significant heat rejection and is typically handled by using a cold water source. Traditionally, lakes and rivers were used to reject this heat because they provide an enormous capacity to accept and remove heat. However, water consumption, and the adverse effect thereof, is a concern in such heat rejection systems.
Some designs employ a radiator-like serpentine of pipes and heat fins that carry exhaust steam within, while sprinklers spray water mist over their outer surface, thereby cooling the steam and heating the environmental water. The supplied cooling water, which is now heated, cools naturally by accelerated evaporation that places large amounts of steam and humidity into the air. Again, the consumption of water is also an undesirable aspect of such designs.
In a solar power collection system, the supply heat is an indigenous component to the environment and is a natural component of the solar power collection system. The surface area of the solar power collection system, which is used to collect solar thermal energy as a source to a heat engine, is sufficient to accept and hold any rejected heat. More importantly, the eco-system of the area which supports the solar power collection system depends upon it.
An example of a heat engine may be found in a current method for the large scale collection and concentration of solar thermal energy. The heat engine uses an array of heliostat mirrors to reflect the sun's rays to a central receiver. By utilizing multiple heliostat mirrors in the array, each one reflecting to a common point, concentration of solar thermal energy is achieved.
In these known systems, heliostat mirrors are set in a fixed position surrounding the tower. The mirror surfaces are typically controlled in two degrees of motion to position the surface of the mirror with respect to the tower. Each heliostat mirror has a control system which tracks the motion of the sun with respect to the centrally located receiver. The mirror is continuously moved to maintain the solar reflection from the surface of the mirror onto the receiver. The purpose of positioning the heliostat mirrors being to reflect and direct the sun's rays to a designated central collection point, known as a central target receiver or a power tower. In order to accomplish this, the heliostat mirror requires a surface area of reflective mirror, two axes of motion, a servo motor for each axis of motion and a control system for positional calculation and motion control of the two axes.
There is a need for a solar power collector that is capable of sustaining the rejection of heat.